An apparatus of this type is described in U.S. Pat. No. 4,023,190. In the latter, the papers and pieces of film to be developed are moved with only a quite slight deviation from a continuous conveying plane and due to the dynamic sealing of the processing chambers, at their inlet or outlet opening, a liquid level lying above the conveying plane can be maintained dynamically in the processing chamber, since the circulating pump associated with the processing chamber can supply slightly more processing liquid to the dynamically sealed processing chamber than is lost through the leakage points at the inlet opening and outlet opening.
However, if a developing apparatus of this type is stopped for a relatively long time, for example overnight or for the weekend, or if the apparatus is generally only required at intervals of several days, then when the circulating pump is switched off, on account of the leakage losses at the dynamic seals, the liquid level falls slowly to below the seals. Thus, the conveying means serving for moving the material to be developed are at least partially no longer covered with processing liquid and after the evaporation of water, developer salt or fixer salt remains on the conveying means. After the apparatus is once more set in operation, these salt crusts dissolve only slowly or on the whole no longer completely and then impede the troublefree conveyance and uniform processing of the material to be developed and may lead to scratches on the film.
Further developing apparatus with dynamically sealed processing chambers, filled with liquid, are described for example in U.S. Pat. No. 3,057,282, DE-OS 26 33 145, DE-OS 27 31 045 and DE-PS 33 45 084. For these developing apparatus, the above-described drawbacks are true to the same extent.